Electrogenic, proton-coupled, intestinal dipeptide transport in
herbivorous and carnivorous teleosts.
Thamotharan, M., J. Gomme, V. Zonno, M. Maffia, C. Storelli, and G. A.
Ahearn.
Dept. of Physiology, University of Hawaii, Honolulu, Hawaii 96822,
Dept. of Physiology, University of Copenhagen, Denmark, Laboratorio
di Fisiologia, Universita di Lecce, Italy, Dept. of Zoology,
University of Hawaii, Honolulu, Hawaii 96822
APStracts 2:0311R, 1995.
In both herbivorous tilapia (Oreochromis mossambicus) and carnivorous
rock fish (Sebastes caurinus), intestinal and pyloric cecal brush
border membrane vesicles, 14C-glycylsarcosine (14C-Gly-Sar) uptake
was stimulated by a transmembrane proton gradient. A transmembrane K+
diffusion potential (inside negative) stimulated 14C-Gly-Sar uptake
above that observed with short-circuited vesicles, while an inwardly
-directed Na+radient in both fishes had no effect on peptide uptake.
In tilapia, 14C-Gly-Sar influx occurred by the combination of (1) a
high affinity, saturable, proton-gradient-dependent, carrier system
(Kt = 0.56 +/- 0.08 mM, Jmax = 1945.0 +/- 174.6 pmol/ mg protein/ 10
sec), (2) a low affinity, non-saturable (within 1-10 mM), proton
-gradient-dependent, carrier system (Kns = 4514.0 +/- 28.1 pmol/ mg
protein/ 10 sec/ mM), and (3) a diffusional component accounting for
less than 10% of total influx within the concentration range tested.
Influx (10 sec) of 1-10 mM 14C-Gly-Sar in tilapia intestine was
significantly (P<0.01) inhibited by 10 mM DEP
(diethylpyrocarbonate), a specific inhibitor of proton-coupled
peptide transport systems. 14C-Gly-Sar influx into tilapia BBMV
showed cis inhibition and trans-stimulation by Gly-Pro, suggesting
that 14C-Gly-Sar and Gly-Pro shared the same mucosal peptide
transporter in fish. These observations strongly suggest that
intestinal transport of peptides in herbivorous and carnivorous
fishes is proton-gradient-dependent, electrogenic, sodium independent
and qualitatively resembles the peptide transport paradigm proposed
for mammals.
Received 16 May 1994; accepted in final form 26 September 1995.
APS Manuscript Number R261-4.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 November 95